1. Field of the Invention
The apparatus and method of the present invention relates to the connection of a flexible conduit such as a flow line or an electrical cable, or a combination of multiple flowlines and cables commonly known as a flowline bundle, between a subsea structure typically located upon the ocean floor and a moveable floating platform positioned above the subsea structure.
2. Description of the Prior Art
As drilling activities progress into deeper offshore waters, new methods and apparatus need be developed to allow for the economic production of oil and gas reservoirs located in these deeper waters. A floating production system (hereinafter FPS), wherein the FPS is a drilling and production platform carried on a moored but otherwise freely floating semi-submersible vessel, appears to be cost effective for use in water depths just beyond the capabilities of fixed bottom-supported structures, for example, in the 1500 to 3000 foot water depth range. Throughout its operational lifetime such an FPS remains moored above the same general area of the seafloor. In a typical deepwater field development using the FPS, a number of subsea wells therefore may be drilled vertically from the FPS within an area defined on the bottom having a radius of approximately 15% of the water depth.
As can be imagined, a problem exists of how to hook up flow lines between the subsea wells and the FPS, in order to carry the flow of production from the on-bottom wells to the FPS floating on the water surface. Typically in this situation, a vertically tensioned riser has been used to connect the subsea wellhead to the FPS. Such a vertically riser consists of a long flowline bundle attached at its lower end to the subsea wellhead and tensioned at its upper end by means of tensioners carried on the FPS. The riser tensioning system used to apply the tension to the entire riser in order to prevent the buckling of the riser justifiably very expensive to install and maintain over the life of a typical production field, for example, 30 years. Such a riser tensioning system must remain in the active state over the entire 30 year life of production from the field in order to prevent damage to the riser. The probability of such a system functioning flawlessly for 30 years is minimal at best, thereby enhancing the chances of a well blowout with associated risks to the FPS, its crew and equipment.
A method and apparatus need be developed therefore that allows a subsea well to be connected in a safe and relatively inexpensive manner to an FPS located substantially vertically above the subsea well location